SMD fuse factory teaches you to know SMD fuse

SMD fuses are mainly used in electronic products such as digital cameras, notebooks, and mobile phones. . . From traditional glass tube fuses to miniature fuses and chip fuses, the focus of their selection is slightly different due to differences in product technology.

The selection of chip fuse involves the following factors:

(1) The normal working current of the circuit. The working current through the fuse should not exceed 75% of the rated current of the fuse.

(2) Pulse, impulse current, surge current, starting current and circuit transient value. SMD fuses pay special attention to this point. Due to the technological reasons brought about by their small size, the impact resistance of SMD fuses is far less than that of glass tube fuses with the same rated current or other larger fuses.

(3) The magnitude of the overload current of the circuit and the shortest and longest time that the overload current exists. Usually need to use the combination of oscilloscope test and theoretical calculation to judge the magnitude of the overload current. The basic requirement for the fuse is that it cannot be broken when it should not be broken (for example, when a surge current occurs), and it must be broken within an appropriate time when it should be broken (for example, when an overload current that needs to be cut off occurs).

(4) Resistance. The resistance of the chip fuse has a certain influence on some circuits: if a fuse with too large internal resistance is installed in some circuits, it will affect the system parameters of the circuit and make the circuit unable to work normally.

(5) The ambient temperature of the fuse. When chip fuses are used in portable equipment, the temperature rise of the fuse should be properly considered, that is, the reduction of the rated current of the fuse should be considered. When the fuse is working, the ambient temperature should be within the specified operating temperature range. When the ambient temperature around the fuse exceeds 25°C, it should be degraded and used according to the temperature reduction curve.

(6) The external voltage applied to the fuse. Usually chip fuse is used in portable equipment, and the circuit working voltage is generally not high. As long as the rated voltage of the chip fuse is higher than the working voltage of the circuit, you can use it with confidence.

(7) Product certification. For example, export to North America must have UL or CSA certification. At present, products exported to Europe also need to comply with the EU's RoHS directive, which is commonly referred to as SGS and other environmental certifications.